The goal of the proposed Rheumatic Diseases Core Center is to promote and foster cutting-edge research that will further the understanding of the pathophysiologies of the pediatric rheumatic diseases and lead to novel therapeutic approaches to the treatment of these diseases. Interaction between basic science and clinical research efforts are emphasized The individual core components have been carefully chosen to maximize the opportunities to achieve this goal. Criteria for selecting these cores included (1) exciting novel technologies with potential to exploit the existing strong interactions between members of the research base and promote new interdisciplinary efforts, (2) provision of unique resources not readily available to individual investigators, (3) usefulness to a significant number of research base members, (4) promotion of cost effectiveness among investigators, (5) institutional commitment to the core technologies. In addition to interacting with members of the research base, significant interactions between the core components is anticipated as well. This will result in additional synergistic impact to the Center beyond the individual effects of each core component. The Core components will allow investigators in the rheumatic diseases a comprehensive set of tools to further the study of these conditions. These include a unique set of pediatric rheumatic tissues (Pediatric Rheumatology Tissue Repository Core), the ability to measure clinical parameters of disease in humans and animals in a more sensitive and quantitative manner (Magnetic Resonance Imaging Core), the tools to quantitate soluble mediators (Cytokine Quantitation Core) and to isolate and characterize cells (Cell Isolation and Phenotyping Core) involved in autoimmunity, and finally, the tools to process these data at a level of sophistication not previously possible (Pediatric Rheumatic Diseases Research Informatics Core). Two Pilot and Feasibility studies are included: 1) Interleukin 15 and vascular endothelial cell activation in juvenile rheumatoid arthritis synovium. 2) Angiotensin converting enzyme inhibitors in lupus nephritis: effect on TGF-beta and autoantibody production.